BInary search algorithm

Being a beginner in algorithms I am not able to understand how should i proceed with a problem which uses binary search algorithm?
the problem that i am facing is i am not able to idntify the predicate for the sample space.
I read the tutorials of Topcoders but still i am facing difficulty?Can any one help me in this

what kind of difficulties can you please elaborate?

Actually i can understand your problem because we are in the same boat :p.I also face same difficulty.I can suggest you AGGRESSIVE COW from spoj a nice problem and you can also see on answer on quora why we used binary search there.